1. Technical Field
The present invention relates to spectrophotometers.
2. Related Art
In the past, a tunable interference filter having a pair of reflecting coatings facing each other and extracting a light of a predetermined wavelength from a light to be measured by changing the distance between the reflecting coatings has been known. Moreover, a spectrophotometer measuring the spectrum of a light to be measured by using such a tunable interference filter has been known (see, for example, JP-A-7-243963 (Patent Document 1)).
The optical resonator (the tunable interference filter) described in Patent Document 1 includes a first substrate having a recessed portion formed on the surface thereof and a second substrate, the second substrate being bonded to the first substrate in such a way as to close the inside of the recessed portion of the first substrate. Moreover, high reflecting coatings facing each other and electrodes adjusting the gap (the inter-reflecting coating gap) between the reflecting coatings are provided on the bottom of the recessed portion of the first substrate and the face of the second substrate facing the recessed portion. In addition, on the second substrate, a thick portion and a thin portion are provided in a region facing the recessed portion, and the thick portion can move toward or away from the recessed portion as a result of bending of the thin portion.
In such a tunable interference filter, it is possible to deform the thin portion of a diaphragm by applying a voltage between the electrodes, and it is possible to adjust the inter-reflecting coating gap by moving the thick portion toward or away from a glass substrate.
Incidentally, when a light of a target wavelength is extracted by the tunable interference filter described above, a voltage according to the target wavelength is applied between the electrodes. At this time, since the electrostatic attraction associated with the application of a voltage and an elastic force of the thin portion of the second substrate act on the thick portion of the second substrate, the thick portion vibrates.
Therefore, in the past, to measure a light of a target wavelength with high accuracy, the spectrophotometer using such a tunable interference filter has waited until the thick portion stops vibrating and performed light amount measurement after the thick portion stops vibrating. This increases the time required to perform measurement.
In particular, in the spectrophotometer, it is necessary to measure the amount of light at each wavelength by sequentially changing a wavelength to be measured in a predetermined wavelength range. As a result, when the above-described waiting time is provided for each of all the objects to be measured, the time required to perform measurement is further increased.